[NFC] Replace uses of Type::getPointerTo

Replace some uses of `Type::getPointerTo` via 2 ways
* Remove entirely if it's only used to support an unnecessary bitcast
  (remove the bitcast as well).
* Replace with `PointerType::get`/`PointerType::getUnqual`

NFC opaque pointer clean-up effort.

GitOrigin-RevId: 204883623ebd194669fc54435222e5bfb245b011
1 file changed